The present application relates to a display device, a display apparatus, and method of adjusting a color shift of white light in same. More particularly, the present application relates to a display device such as an organic EL device having an optical cavity structure and a display apparatus such as an organic EL display using the display device.
In recent years, an organic EL display using organic EL (Electro Luminescence) devices has been noted as one of the display apparatuses that is replacing liquid crystal displays. The organic EL display is a spontaneous emission-type display where an organic material itself emits light when current flows therethrough. Therefore, the organic EL display has excellent characteristics in that it is not necessary to have a backlight and exhibits excellent color reproduction properties, high contrast, fast response properties appropriate for moving pictures, and a wide viewing angle.
An organic EL device used in the organic EL display has a structure in which an organic layer is disposed between an anode and a cathode, holes are injected from the anode to the organic layer and electrons are injected from the cathode to the organic layer, whereby light is emitted from a portion where hole-electron recombination takes place. The organic layer has a stacked structure, for example, including a light emitting layer in the portion where hole-electron recombination takes place, a hole transport layer provided for accepting and transporting holes from the anode to the light emitting layer, an electron transport layer provided for accepting and transporting electrons from the cathode to the light emitting layer, and the like.
In the field of the organic EL display, a display is in practical use in which the organic layer and one of the anode and cathode, and the like form a cavity structure, thus improving optical output power, reducing power consumption, raising color purity with the use of a multiple interference filter, and widening a color-reproduction range. Examples of such an organic EL display are disclosed in JP-A-2007-294421, JP-A-2007-134345, JP-A-2008-524819, and JP-A-2008-523551, for example.
The organic EL display having a cavity structure is able to raise color purity and widen a color-reproduction range since it is possible to extract light whose peak spectral intensity is high and whose width is narrow. On the other hand, in the organic EL display having a cavity structure, when the peak spectral width of the extracted light is narrowed, viewing-angle dependency increases. For example, when an emission surface is viewed from an oblique direction, the wavelength of light shifts greatly and the emission intensity decreases.
To improve the viewing-angle dependency, JP-A-2008-140714, for example, discloses a technique of providing an interference cancellation layer which is thicker than the principal emission wavelength of the light emitting layer and has a non-uniform thickness and which is capable of canceling possible optical interference between an optically transparent reflective electrode and a reflective layer. Moreover, WO2005/094130, for example, discloses a technique of forming a layer having light-scattering and light-reflecting properties so as to reduce angle dependency of emission luminance and emission colors.
Furthermore, JP-B-3508741, for example, discloses a technique of improving a white viewing angle when multiple interference effect is used. According to this technique, by shifting the peak wavelength of an internal emission spectrum relative to the peak wavelength of a multiple interference filter spectrum, the viewing-angle dependency of white which is very easily perceived visually is suppressed to an acceptable level that does not cause any problem in practical use.